In vitro cellular and tissue models for various drug testing and screening experiments are often central to the development of novel therapeutics in the pharmaceutical industry. Currently, however, most in vitro studies are still performed under conventional two-dimensional (2D) cell culture systems, which are often not physiological models for functional tissues and tumors. Therefore, drug studies involving such models may not produce accurate readouts. To obtain more meaningful results, in vivo studies involving animals are often utilized. However, one obvious drawback of in vivo studies is the time-consuming and expensive nature of these experiments. To bridge this gap between the non-physiological conventional 2D models and in vivo experiments, three-dimensional (3D) in vitro models that provide more therapeutically predictive and physiologically relevant results for drug testing and screening in the pharmaceutical industry are needed. One way to create 3D cell culture models is through the formation of spheroids, or 3D clusters or aggregates of cells.
Scaling up of spheroid culture in a manner suitable for certain applications such as high-throughput screening and testing has several drawbacks. Traditional spheroid formation involves cultivation of suspended cells in hanging drops on the underside of a Petri dish lid. This process requires inverting of the lid following placement of the drops. As a result, the drops are susceptible to perturbation, resulting in falling, spreading, and merging with neighboring drops. Although inexpensive, this method is labor-intensive, does not permit efficient scalable production, and is not compatible with automated instruments for high-throughput screening. Because it is difficult to perform media exchange without damaging the spheroids, this method usually requires another labor-intensive step of transferring the spheroids manually, one by one, to a multi-well culture plate for longer-term culture, treatment, analysis, and harvest.
An alternative is to induce the formation of spheroids under continuous agitation of cell suspension in bioreactors, such as spinner flasks and rotary culture vessels. This method requires the consumption of large quantities of culture media. It also requires specialized equipment and the size and uniformity of the spheroids are hard to control. The high variability in spheroids prohibits their use in many applications.
Methods are also available to produce spheroids using 3D microwell structures and planar micropatterns. However, these methods require specialized and expensive equipment for generating the microwell structures and micropatterns. Moreover, since a plurality of spheroids is cultured within one fluid compartment, the spheroids cannot be individually monitored, manipulated, and treated with testing compounds. The difficulty of performing analysis on individual spheroids before and after treatment also makes these methods unsuitable for certain applications, for example, drug testing and screening applications.
Other recent advances include microfluidic devices designed to generate and manipulate spheroids. However, these devices are expensive to design and produce. In addition, these devices are not suitable for long-term culture of spheroids, not chemically compatible with certain drugs, and not compatible with automated instruments for performing high-throughput screening.
To address problems in the art, there is a need for the devices, methods and/or systems disclosed herein.